Teardown: Inside the art of pulse oximetry

Few disciplines can turn the cold science of metrology into pure art as quickly as medical diagnostics. Its practitioners transcend the confines of biology, chemistry and physics, borrowing from each discipline—and stretching the limits of technology—first to divine what to measure, then to make the measurements and extract the desired information from the data.

Transformation of the raw values into valuable metrics requires the development and implementation of special signal-processing algorithms. By melding what is already known with carefully thought-out assumptions that are based on years of research and experiential data, such algorithms often form the intellectual property heart of advanced diagnostic equipment.

Certainly, that holds true for Masimo's Radical-7 Signal Extraction Pulse-CO Oximeter. At the crossroads of science and art , the Radical-7 combines patented signal-extraction algorithms and advanced spectrographic and signal-acquisition technology in an efficient and intuitive design that takes blood analysis out of the lab and into the field, accelerating the time to diagnosis (and thus to treatment).

The Radical-7 weighs in at around $6,000 in its baseline configuration, rising to approximately $15,000 for all the bells and whistles, but those whose lives it has helped save through its in vivo, noninvasive methodology would consider that a steal. The system can extract an accurate signal even when the subject is moving, and it is undaunted by variations in bone density and skin pigmentation.

Masimo's Radical-7 takes blood analysis out of the lab and into the field.

"It's a no-brainer to take a vial of blood, put it in a test tube or cuvette, put that in a spectrophotometer and get [the desired] information," said Anand Sampath, Masimo's executive vice president of engineering. "Physicists and chemists know how to do this on the bench." It's another matter, Sampath said, "to do it in vivo, where the blood is actually pulsating and you have all kinds of artifacts and tissues."

But there are times when in vivo testing is the best, and perhaps the only, option. In an office tower fire, for example, portable equipment for noninvasive analysis would allow large numbers of people to be tested on site for carbon monoxide (CO) poisoning.

"There's no way to do it without a device like ours," said Sampath. "You'd literally have to take them to a hospital and draw blood, and it would take hours [to get results]. Meanwhile the damage is done."

Now, he said, "it's something a guy in an ambulance can do."

Sampath pointed to the ability of Masimo's systems to monitor a moving subject, compensating for the artifacts that such movement introduces. Invented by Masimo in 1996 (and covered in U.S. Patent Nos. 6,770,028, 6,658,276, 6,157,850, 6,002,952 5,769,785, and 5,758,644, among others), this capability applies across all situations but is particularly helpful in the case of premature babies, whose blood oxygen levels need constant monitoring but who are unlikely to remain still for the procedure. Until the advent of effective in vivo testing, such infants were sometimes given too much oxygen, causing retinopathy of prematurity (ROP); severe cases often resulted in blindness, according to Sampath.

I was a first gen paramedic, left the biz after 21 yrs and Pulse Ox was just getting on board ambulances at the time 93-94. This will truly be an important improvement and save a lot of time especially in ICU's and CCU's. In some cases the time it takes for a blood test is the time it takes to lose a patient. The 15k version will easily pay for itself in the first year of use.
Hooray for Masimo..and thanks for the helpful tech!
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